Materials obtained in the study of conditions for contacting acute enteric infections of uncertain etiology, based on the analysis of the age structure of patients, the structure of clinical diagnoses and the monthly dynamics of cases registered in one of the districts of Moscow for 3 years (1984-1986), are presented. An important role of the alimentary factor in the spread acute enteric infections of uncertain etiology among the population of different age groups and everyday contacts in the spread of such infections among young children has been shown. The authors put forward a suggestion concerning the formation of natural immunity to infective agents, serving as etiological factors in the development of enteric infections of uncertain etiology, in children of preschool age.